We do not recommend setting the backlash greater than 90 arc-
seconds (1.5 arc-minutes). It won't improve the life of the
mechanism, and could result in chatter during machine operations.
About Backlash
Backlash is an important element in managing overall accuracy. On
a rotary table, a number of internal sliding surfaces depend on a
hydrodynamic oil film for low friction and long service life. The
adjustment of clearances between these surfaces helps to achieve
precision and extends service life — much like the adjustment of the
lead screw nut and gibs on a mill or a lathe.
If the backlash is adjusted to zero, the worm screw (and other parts)
are subjected to excessive wear and friction — which may lead to
stalling of the rotary table. As the worm screw turns, the oil shears
off at the gear interface, and provides no film to protect against
metal-to-metal wear.
5.1.2 Adjust the Lock Nut
You must adjust the lock nut to adjust for wear in the worm gear.
1. Loosen the socket head cap screw and the set screw on the
motor coupling. Do not remove the screws.
2. Remove the four mounting screws securing the motor to the
motor mount.
3. Remove the motor — with the coupling still attached — from
the motor mount.
4. Put grease on the back side of the spacer.
5. Use two spanner wrenches to tighten (or loosen) the lock
nuts.
Figure 5-4: Example of tightening the lock nuts with two
spanner wrenches.
6. Adjust the spacer nut so that — when turned by hand — there
is no axial play in the worm shaft, and so that the shaft moves
freely. Do not over-tighten the lock nut.
Figure 5-5: Example of turning the spacer nut by hand.
5.1.3 Adjust the Rotary Table
To test for correct axial adjustment:
1. Disengage the worm.
2. Rotate the table by hand. You should feel a slight drag. If you
do not feel a drag, do the following:
a. Use a flat-head screwdriver to loosen the three screws in
the retaining plate two turns.
b. Use an Adjustable Pin Spanner Wrench (PN 31118) to
tighten or loosen the retaining plate.
Figure 5-6: Retaining plate on the rotary table.
c. Rotate the plate clockwise to increase drag, or
counterclockwise to decrease drag.
5.1.4 Examine the 4th Axis for Coolant Resistance
To make sure that the 4th Axis is resistant to coolant, regularly do
the following:
l
Use thread seal tape to seal the set screw on the motor
mount.
Page 10
©Tormach® 2019
Specifications subject to change without notice.
tormach.com
TD10552: Owner's Guide: 4th Axis (0919A)
TECHNICAL DOCUMENT
